This proposal aims to determine the potential for selfish genes, AKA homing endonucleases, to serve as a method of dispersing and fixing genes into natural mosquito populations that reduce the vector competence of mosquitoes to transmit pathogens, such as the causative agents of dengue fever and malaria. In the first aim of this proposal we seek to determine the ability of various homing endonucleases to generate dsDNA breaks using a two-plasmid based assay. This assay has been designed so that successful cutting by the homing endonuclease will result in the loss of a negative selectable marker. Plasmid-based assays will be conducted in both cultured mosquito cells as well as in live embryos. In the second aim we seek to determine the rate at which homing endonucleases can excise a transgene from the mosquito genome. A marker gene flanked by homing endonuclease recognition sites will be inserted into the mosquito genome, followed by the introduction of a homing endonuclease which should excise the marker. Homing endonucleases found to be functional in both plasmid-based assays and transgene excision assays will serve as the foundation for future work at adapting homing endonucleases as a method of gene drive. Public health relevance: This work is part of a larger, ongoing strategy to control human pathogens using genetics. Such a genetic control strategy is founded on the hypothesis that reduced/ablated vector competence will result in a corresponding reduction/elimination of human disease, and is based on three elements: the development of anti-pathogen effector genes, the ability to introduce effector genes into mosquito vectors, and the ability to spread these effector genes into wild populations. The first two elements have seen substantial progress in the past decade, and this proposal is designed complement this work so genetic control strategies can become a reality in effecting and improving public health outcomes due to vector-borne diseases. [unreadable] [unreadable] [unreadable]